An intermittent dynamo linked to high-titanium volcanism on the Moon

Abstract The history of the lunar magnetic field is a longstanding controversy. Many palaeomagnetic studies provide evidence for either a persistent, weak magnetic field or the lack of an intrinsic magnetic field between 1.020 and 3.580 billion years ago. However, for the period between 3.580 and 3.854 billion years ago, palaeomagnetic studies have recovered strong intrinsic fields (>40 µT) distributed among weak or null intensity measurements. Crustal magnetic anomalies from this period have also been interpreted as evidence for the presence of both strong and weak magnetic fields. Here we explore potential links between published palaeointensity, rock magnetic and geochemical data for lunar basalts. We find there is a statistically significant relationship only between recovered palaeointensity and the titanium content of lunar basalts. By modelling the heat flux across the core–mantle boundary, we suggest that there is a causal link between lunar dynamo generation and the eruption of high-titanium basalts. Such a link may result from the intermittent melting of ilmenite-bearing cumulates at the core–mantle boundary. The coincidence of these rare events probably reflects sampling bias near high-titanium basaltic terranes.